Electric heater.



H. AJBLACK.

ELECTRIC HEATER: APPLICATION man JUNE II, 1917.

Patented Nov. 20, 1917.

Inventor Horatio ABIELCK nona'rro A. BLACK, 91* TOPEKA, ansas.

ELECTRIC HEATER.

Specification of Letters Patent.

Patented Nov. 20, 1917.

Application filed June 11, 1917. S criaI No. 173,943.

To all whom it may concern:

and for a well propor Be it known that I, HORATIO A. BLACK, a citizen of the United States, resic'ling at To ieka, in the county of Shawnee and State of (ansas, have invented certain new and useful Improvements in Electric Heaters, of which the following is a specification.

My invention is an electrical heating element preferably of the small portable type used for heating ovens and for other domestic and industrial purposes.

Objects of my invention are to improve generally upon heating elements of the kind stated especially in the matter ofa greater retention of the heat and of a cheaper construction and a more convenient and eflicient arrangement of parts. 1

The invention relates in particular to improving the heating core by wholly embedding the resistance wire within the core body which is a non-conductor of both electricity and heat, so that the wire is protected against cross circuits and the entire core will be intensely heated; also it relates in par ticular to an improved shell, container or envelop for the core, made of special com: position forprotecting it against breakage tioned transmission and retention of the heat generated in the core.

And my invention comprisesthe certain arts, improvements and combinations here mafter set forth and claimed.

In the drawings accompanying and forming part of this specification and in the description of the drawings, I have shown my invention in its preferred form and what I deem to be the best mode of applying the principles thereof; but it is to be unders that, within the scope of the appended claims, I contemplate changes in form, proportions and materials, the transposition of parts and the substitution of equivalent members, without departing from the spirit of my invention.

Figure 1 is a central longitudinal sectional elevation of the complete device made in accordance with the principles ofrny invention, on a plane indloated by the line 11 in Fig. 3. Fig. 2 is a view of the left-hand end, as '"viewed in Fig. 1, with dotted outlines of certain interior parts. Fig. 3 is a transverse sectional elevation on a plane indicated by the line 3-3 in Fig. 1.

Similar reference characters indicate similar parts throughout the three views.

The body of the core 4 may be of any suitable or corvenient shape, preferably round in cross section and of convenient length, one end being incased in a suitable cap 5 which serves as a handle. The two line wires 6 extend into the body through the hole 7 in the cap and are connected with the conductors 8 which in turn are connect ed with opposite ends of the resistance,

which is preferably in the form of a resistance wire 9 coiled around the core.

The composition of the body may be of any suitable non-conducting substances. I 1

prefer and suggest the following: Plaster Paris, two parts; heavy carbonate of magnesia, two parts;-sand, one part; ground glass, these parts being mixed with water, an

sufiicient of a 15% solution of silicate of soda being added to insure its proper hardening. While in the plastic state, the core is formed with the wires embedded therein and the cap applied thereon; the resistance coil is wrapped around it and fastened to the terminals, as shown. While still in the plastic state, the core is covered with a rather thin coating of the same mixture, as shown at 10, so to embed the resistance coil completely within the core; the coating 10 being then integral with anda solid part of the core.

With the device just mentioned, which has been properly hardened, the resistance will cause the core to become intensely hot, at least the coating becoming red-hot over the coil.

A shell 11 is provided of cylindrical form, open at one end and closed at the other, to fit. rather snugly over the core, being slipped thereonto from the end opposite the handle. The shell is made of the same composition as the core, with the addition of about 1} in volume of metal particles, such as iron filings, thorou hly mixed therewith, and the shell is pre erably hardened and baked, and may be finished with a glazed surface.

The shell is obviously very cheap to make. Also it is quite substantial; but, if broken, can be easily replaced at a. minimum of expense. It protects the core against breakage and from cracking as in case water is spilled on it.

The main body of the shell is' a non-conductor of heat, and therefore tends to confine the heat within the core; and the addione-half part; pipe clay, two partstion of the iron filings permits the transmission therethrough of the heat only in restricted volume; hence the suitable combination of heat retention and heat transmission is obtained. The metal being finely comminuted and thoroughly mixed in the plaster and main body of the shell will not crack the shell by reason of contraction and expansion under varyin heat conditions.

Having thus describe my invention, what claim 1s:

1. The combination of a core non-conductive of heat and electricity, a cap formed on one end of said core and forming a I handle, a resistance coil embedded in said core near the surface thereof but not exposed, Wiring embedded in said core and connected with the resistance wire and passmg; in through said" cap, and a cylindrical shell open at one end and closed at the other and fitting over and enveloping said core, said shell being made of material that is non-conductive of heat with the admixture of a portion of difl'used iron filings.

2. The combination of a core non-conductive of heat and electricit a cap formed on one end of said core and forming a handle, a resistance embedded in said core near the surface but not exposed, wiring embedded in the resistance, and a shell fitted over said core and comprising material that is nonconductive of heat with the diffused addition of finely comminuted metal particles.

3. The combination of a heating core and a shell therefor, said shell being made of material that is non-conductive of heat with the addition of difi'used finely comminuted particles of material that is conductive of heat.

4. An envelop for an electrical heating core, said covering being made of material that is non-conductive of heat with the addi tion of diffused finely comminuted particles of material that is conductive of heat.

In testimony whereof I have hereunto aifixed my signature.

HORATIO A. BLACK. 

